Fire alarm device

ABSTRACT

A fire alarm device including thermostat means operably connected to conductor means whereby a fire condition may activate the thermostat for providing a signal current to activate an alarm in electrical connection with the thermostat. The thermostat includes a normally open switch means having a pair of downwardly depending conducting elements extending therefrom. Each member of the pair of conducting elements is adapted to contact in electrically conducting fashion a member of a pair of current carrying conductors whereby closing of the switch due to exposure to fire may activate an alarm. In a preferred instance the conducting elements are in contact with a pair of barb-bearing electrical contacts in a hinged, channel forming receptacle. Closing of the receptacle about its hinge over a conventional electrical cord including a pair of current carrying wires forces the barbs into mechanical and electrical contact with the wires. In that fashion, the thermostat means is rapidly and efficiently operably contacted with the wires. Each hinged, channel formed receptacle includes means, such as bores, therein through which testing means, such as electrical leads to a voltmeter or the like, may be inserted for testing the connection between a fire alarm device and current carrying wires. Additionally, a fire alarm system is provided including a plurality of the foregoing fire alarm devices connected in parallel along a length of conduit and including appropriate alarm devices therefor.

United States Patent 91 Jamison Jan. 15, 1974 FIRE ALARM DEVICE [75]Inventor: Will B. Jamison, Bethel Park, Pa.

[73] Assignee: Consolidated Coal Company,

Pittsburgh, Pa.

221 Filed: Oct. 12, 1971 211 Appl. No.: 188,412

[521 US. Cl 340/227.1, 337/362, 337/381, 339/99 R [51] Int. Cl. G08b17/06 [58] Field of Search 340/227.1; 337/362, 337/381, 333, 415;339/98, 99 R [56] References Cited UNITED STATES PATENTS 3,263,0497/1966 Doherty, .lr 337/381 2,735,078 2/1956 Greenbaum.... 339/99 R2,132,918 10/1933 Allen' 337/381 1,927,744 9/1933 Jones 340/227.l

2,954,447 9/1960 Bolesky et al. 337/333 3,663,924 5/1972 Gerlat 339/99 R2,779,842 l/1957 Walker 337/415 1 2,204,237 6/1940 Slack et al. 337/412Primary Examiner-John W. Caldwell Assistant Examiner-Glen R. Swann, lllAttorney-D. Leigh Fowler, Jr. et a1.

5 7 ABSTRACT A fire alarm device including thermostat means operasllt\\bly connected to conductor means whereby a fire condition may activatethe thermostat for providing a signal current to activate an alarm inelectrical connection with the thermostat. The thermostat includes anormally open switch means having a pair of downwardly dependingconducting elements extending therefrom. Each member of the pair ofconducting elements is adapted tocontact in electrically conductingfashion a member of a pair of current carrying conductors wherebyclosing of the switch due to exposure to fire may activate an alarm. Ina preferred instance the conducting elements are in contact with a pairof barb-bearing electrical contacts in a hinged, channel formingreceptacle. Closing of the receptacle about its hinge over aconventional electrical cord including a pair of current carrying wiresforces the barbs into mechanical and electrical contact with the wires.in that fashion, the thermostat means is rapidly and efficientlyoperably contacted with the wires. Each hinged, channel formedreceptacle includes means, such as bores, therein through which testingmeans, such as electrical leads to a voltmeter or the like, may beinserted for testing the connection between a firealarm device andcurrent carrying wires. Additionally, a fire alarm system is providedincluding a plurality of the foregoing fire alarm devices connected inparallel along a length of conduit and including appropriate alarmdevices therefor.

8 Claims, 3 Drawing Figures 1 1 72 LYJ PAIENTEUJAH 1 51914 POWER SUPPLFIRE ALARM DEVICE BACKGROUND OF THE INVENTION This invention relates toa fire alarm device, and more particularly to an improved fire alarmdevice which may be rapidly and efficiently connected to a pair ofcurrent carrying conductors.

Fire alarm systems comprising a plurality of fire detectors locatedalong a pair of spaced-apart, insulated conductors are well known in theart. Fire detectors in such applications generally are heat responsivewhereby the heat from a flame near the fire detector will operate insome fashion to complete a circuit between a power source and an alarmdevice. For example, U. S. Pat. No. 2,l86,l l2 discloses a fire alarmsystem wherein a multiplicity of contact fuses are provided along acurrent carrying line composed of a pair of current carrying wires.There, the fuses are heatdestructable whereby burning of the fusematerial may result in a complete electrical curcuit to activate analarm device. The circuitry disclosed in the above patent cannot bechecked for continuity between the contact fuses without closing thecircuit by connecting the respective conductors. Further, the activationof the alarm device is dependent upon combustion of the materialseparating the conductors rather than being activated by an elevatedtemperature. U. S. Pat. No. 2,204,237 discloses a thermostat connectedin parallel between a pair of current carrying wires disposed between apower source and an alarm device such as a bell. The thermostat includesa heat responsive element or elements whereby exposure to heat from aflame may activate the thermostat to close an internal switch forcompleting the alarm circuit. The preferred means for activating theinternal switch comprises the heat destruction of a fusible metal, suchas Woods metal, in a spring loaded switch. U. S. Pat. No; 2,204,237 isprimarily concerned with the provision of a prefabricated alarm cablewherein the thermostats are built into a current carrying cable systemand entails elaborate, rather expensive manufacturing techniquesincluding the splitting of an electrical cord, installation of thethermostat device, and reinsulating the installed device. Also, evenafter assembly or fabrication, there is no assurance that the pins orbarbs of the thermostat are in contact with the metallic conductors inthe wires. There are no provisions for determining this 'without fusingone of the retaining strips in the thermostat and destroying the futureeffectiveness of the thermostat as a temperature responsive device. U.S. Pat. No. 2,779,842 discloses a fire alarm system wherein a pluralityof barb-bearing electrical contacts depending from a conductor encasedin a plastic insulator are provided. The barb-bearing devices areadapted to be-positioned in overlying fashion upon a current carrying,insulated wire and forced into contact therewith whereby the donductingbarbs may penetrate the insulation to come into contact with the wires.Those devices are provided along a length of a pairof insulated currentcarrying wires in overlapping pairs whereby melting of the plasticinsulation thereon may produce a current flow between the currentcarrying conductors which may be sensed in a conventional fashion andemployed as a signal to activate an alarm device. The thermoplasticinsulating material there employed has a relatively low melting point,such as 140F. so that it will melt or close and accurate temperatureresponse for a fire alarm device is required. Moreover, thethermoplastic material can melt and cause the device to respond towidely different temperatures depending upon the rate of heating of thedevice. Again, as in U.S. Pat. No. 2,204,237, barbs or prongs on thethermostatic elements pierce the insulation of the conductors and mustcontact the metallic wire to be effective. The only way to determine ifthe device is operable and the barbs are in contact with the metallicconductor is to melt the thermoplastic insulating material. This againdestroys the temperature responsive device and prevents future use ofthat device. Such is also the case with the first mentioned fused deviceof U. S. Pat. No. 2,l86,l 12.

This invention provides an improved fire alarm device, a multiplicity ofwhich may be placed along a pair of conducting wires in parallelconnection therewith, in a rapid and efficient manner. The inventionfurther provides a fire alarm device of the type described which may bereadily positioned in a fire alarm circuit, and which may be rapidly andeffectively tested without either activating or destroying the firealarm device. Moreover, the invention provides a fire alarm device whichresponds accurately and efficiently at its fixed temperature rating withlittle or no danger of false alarms. Additionally, the fire alarm deviceof the invention is not self-destructable,and may be reused insubsequent applications. And in one aspect, the invention provides afire alarm system which may not only accurately report fireconditions,but will also signal a system failure, i.e., a power loss, cable break,etc. Other advantages of the invention will become apparent as thisspecification proceeds.

SUMMARY OF THE INVENTION This invention provides an improved fire alarmdevice including thermostat means in operable contact with conductormeans whereby a fire condition may activate the thermostat for providinga signal current to an alarm device. The thermostat means includes anintegral, normally open switch including a pair of depending conductingelements. Each member of the pair of conducting elements is operablyelectrically con- -nected with a member of a pair of .spaced, insulatedcurrent carrying conductors or wires, whereby closing of the switch dueto exposure to fire may activate an alarm device. The thermostat meansincludes a heat sensitive actuator for closing the switch. A preferredactuator comprises a bimetallic strip in operable contact with aninsulated switch operator whereby distortion of the bimetallic stripupon exposure to a preselected temperature may activate said operatorfor closing the switch to complete a circuit for operating an alarm.

In a preferred instance, the depending conducting elements of thethermostat are in contact with a pair of barb-bearing electricalcontacts in a hinged, channel forming receptacle adapted to receive aconventional electrical cord including a pair of spaced, insulatedcurrent carrying wires. Closing of the channel forming receptacle aboutthe electrical cord forces the barbbearing electrical contacts intomechanical and electrical contact with the wires. In that fashion, thethermostat means may be rapidly and efficiently contacted with the pairof wires in a fire alarm system. Each hinged, channel forming receptacleincludes means by which the fire alarm device may be effectively andrapidly tested without either activating or destroying the fire alarmdevicev Most preferably, bores are provided in the body thereof throughwhich testing means, such as electrical leads to a voltmeter or thelike, may be inserted for testing the connection of the fire alarm device to the conductors.

In a preferred instance, a multiplicity of such fire alarm devices areprovided along a desired length of electrical cord. The current carryingconductors therein and the devices are provided in an electrical circuitincluding both a fire alarm circuit and a current interruption circuitwhereby not only fire conditions but also system failure conditions maybe effectively signaled. Preferably, a pair of relays through whichcurrent in the system flows are provided for selectively activating fireand power failure indicators or alarms.

Other advantages and detailsof the invention will become apparent byreference to the attached drawings and as the following detaileddescription thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a firealarm device according to the invention.

' FIG. 2 is a partial sectional elevation taken along line lI-ll of FIG.1.

FIG. 3 is a circuit diagram illustrating a fire alarm system employingthe fire alarm devices of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIGS. 1and 2, a thermostat, designated generally 10, is provided and includes ahollow cylindrical body portion 12. Body portion 12 preferably comprisesan insulating resinous composition and has mounted thereon, as by fusingor cementing, a circular thin metallic plate 14 including a plurality ofrib-like recesses 16 extending radially outwardly therein. Plate 14comprises a heat transfer plate and will efficiently conduct heatinwardly to thermostat l0. Thermostat has mounted therein a metallicstrip 18 which will, upon exposure to flame or heat, deform in a knownfashion. Strip 18 may be of a conventional composition, such as a knownheat deformable bime- L tallic composition. Strip 18 will deform at aknown temperature in a predictable fashion. Bimetallic strip 18 ismounted in conventional fashion in thermostat 10, as within recessedslots 20 provided within the head portion 22 thereof. Head portion 22 ofthermostat 10 may comprise various compositions, and may be metallic,such as aluminum, steel, etc. or may be a synthetic resinouscomposition, such as a phenolic or epoxy resin. A cap 24 is provided inthermostat 10 having a high coefficient of heat transfer whereby heat,as from a flame, may be rapidly transmitted to metallic strip 18.Suitable cap materials comprise thin sheets of copper or aluminum.

Thermostat l0 additionally includes a normally open switch 26 in bodyportion 12 thereof. In FIG. 2, switch 26 includes a pair of electricallyconductive strips 28 and 30. Strips 28 and 30 may comprise commonelectrically conductive compositions, such as copper or softberyllium-copper alloy. Strip.28 is bent inwardly at an angle away fromthe vertical, but less than the horizontal, and includes a contact point29 at the end thereof. Strip 30 has a contact point 3| at the endthereof and is bent inwardly substantially to the horizontal whereby thenormal position of contact points 29 and 31 in body portion 12 ofthermostat 10 is somewhat spaced apart. Metallic strip 18 is operablyconnected to switch 26 whereby distortion of strip 18 upon exposure to apre determined temperature results in contact of contact points 29 and31 for closing an electrical circuit. An insulated switch operator, oractivator, 32 is operably located between switch 26 and bimetallic strip18. In FIG. 2, switch operator 32 comprises a plastic pin bonded tobimetallic strip 18 and downwardly extending therefrom into contact withmetallic strip 28 near contact point 29 at the end thereof. Strips 28and 30 extend downwardly through the bottom of thermostat 10 into ahinged, channel forming electrical receptacle 40 through appropriateopenings 41 and 42 in the top wall thereof.

Electrical receptacle 40 is substantially as described in U. S. Pat. No.2,735,078 and illustrated in the Fig ures thereof. Receptacle 40comprises hinged interconnected base member 44 and covermember 45, eachformed of a suitable dielectric material, such as an electricallynonconducting plastic such as nylon, phenolic resin, and epoxy resin.Base member 44 of hinged re ceptacle 40 is formed with a transverselyextending U- shaped channel 46 on a central rib-47 adapted to receive anelectrical cord including a pair of conductors 50 embedded in aninsulation 52. Cover member 45 of receptacle 40 includes contact springs54 and 56 each of which comprise a conductive metal such as copper andwhich are formed of a strip of that metal bent backwardly upon itself.Each contact spring additionally includes a barb or prong 58 at an endthereof. Contact springs 54 and 56 are separated and insulated from oneanother by a downwardly depending rib 60 extending from the top wallportion 62 of cover member 45. As can be seen in FIG. 2, closing hingedreceptacle 40 about hinge 64 results in plunging of barbs 58 on therespective contact springs 54 and 56 through insulation 52 and intomechanical and electrical contact with conductors 50. Conductors 50 maycomprise a conventional electrical wire comprising a multiplicity'ofcopper strands. i v I Receptacle 45 is maintained in closed positionwith the aid of a latch spring 66 seated in base member 44 of receptacle40. Latch spring 60 includes an elongated, vertically extending straightportion 68 adapted to pass through a passageway 69 in closure portion 45and bear thereagainst for aiding in maintaining receptacle 40 in 'closedposition.

Downwardly depending metallic strips 28 and 30 of thermostat 10extending into electrical receptacle 40 are adapted to contact contactsprings 54 and 56 respectively. Contacting elements 54 and 56 aresoldered or welded to thermostat strips 28 and 30 respectively forproviding a permanent connection therebetween. In that fashion,thermostat 10 with switch 26 therein is operably electrically connectedto conductors 50 whereby closing of switch 26 uponexposure of the firealarm device to flame may thus complete a circuit and may activate asuitable alarm device.

A pair of spaced-apart bores 70 are provided in base member 44 ofreceptacle 40 leading from within to without the receptacle. Bores 70are provided on either side of rib 47 and are adapted to receive atesting means for testing the electrical connections in the fire alarmdevice shown in FIG. 2. Suitable testing means may comprise a voltmeter72 having a pair of conducting wires 74 operably connected thereto andissuing therefrom. Each member of the pair of wires 74 includes anexposed conducting portion or lead 76 at the end thereof and each isadapted to pass through bores 70 into receptacle 40 into contact withthe spring contacts 54 and 56. In that fashion, the circuitry within thefire alarm device may be rapidly and efficiently tested.

The utility of the device as thus far described in a fire alarm systemaccording to the invention may best be understood by reference tocircuit diagram shown in FIG. 3. There a battery 100 is charged by apower supply, such as an ordinary AC voltage, through a conventionalpower processing unit PP, such as a rectifier, to provide a regulatedconstant DC voltage to the fire alarm circuit. Discharge of battery 100through the power processing unit is prevented by diode 101. The

circuit includes a pair of conductors 50 extending through the area tobe fire protected. Conductors 50 have a plurality of switch-bearingthermostats T T T, in parallel connection therewith. It should beappreciated here that conductors 50 may comprise an ordinary two-wireelectrical cord. The thermostats are placed in the circuit by simplyclosing over the cord a thermostat-bearing receptacle 40, as hereinabovedescribed. A pair of relays R and R are connected in series in thecircuit. Alarms A and A are activated by switches R and R respectively.Alarms A and A may comprise bells, warning lights, etc. as in ordinaryfire alarm systems. Relays R and R and resistor 102 are chosen such thatunder normal conditions a small signal current passes through bothrelays, and the small current operates relay R but not relay R That is,the signal current is sufficient to energize only relay R in the casewhere the signal current is interrupted, for example due to a cablebreak, relay R is de-energized and alarm A is activated to signal asystem failure. In the case of a fire near any one of the plurality ofswitchbearing thermostats, the switch 26 therein will close to therebyshort out" resistor 102 and increase the current to relay R Relay R I isthus energized to seal itself across conductors 50 and thus activatefire alarm A to signal a fire condition. Preferably, a manual resetswitch 104 is provided to return the circuit to a normal condition afterthe thermostats have cooled.

The foregoing has described the invention and certain preferredembodiments thereof. It is to be expressly understood, however, that theinvention is not necessarily limited to the specifc embodimentsdisclosed therein, but may be variouslypracticed within the scope of thefollowing claims.

According to the provisions ofthe patent statutes, 1 have explained theprinciple, preferred construction and mode of operation of my inventionand have illustrated and described what I now-consider to represent itsbest embodiments. However, I desire to have it understood that, withinthe scope of the appended claims,

the invention may be practiced otherwise than as specificallyillustrated and described.

I claim:

l. A fire alarm switch adapted to be electrically connected in parallelbetween a pair of electrical conductors in a two-conductor wirecomprising,

a thermostat operably connected to an electrical re ceptacle,

said thermostat having a normally open electrical switch operablyconnected to heat sensitive means whereby exposure of said thermostat toa predetermined temperature will close said switch,

said electrical switch including a pair of electrically conductiveelements extending therefrom into said electrical receptacle, saidelectrical receptacle having a channel forming receptacle including baseand closure members adapted to be fitted together for forming atransverse channel therethrough for receiving and holding atwo-conductor wire, said electrical receptacle including a pair ofbarbbearing electrically conductive contacts, each one of said pair ofbarb-bearing contacts adapted to mechanically and electrically contactone of said conductors in said two-conductor wire when said base andclosure members are fitted together over a two-conductor wire positionedin said transverse channel therebetween, 1

said electrically conductive elements extending from said electricalswitch in electrical contact with said barb-bearing contacts, and

said fire alarm switch including a pair of spaced openings in saidelectrical receptacle positioned on the opposite side of said electricalreceptacle from said thermostat for receiving separate portions of atesting device for testing the electrical connections between saidelectrically conductive elements extending from said. switch, saidbarb-bearing contacts, and the connection between said barbbearingcontacts and said conductors.

2. The fire alarm switch as set forth in claim 1 wherein said heatsensitive means includes a heat distortable metallic composition.

3. The first alarm switch as set forth in claim 1 wherein saidelectrical switch includes a pair of electrically conductive metallicstrips extending from within to without said thermostat, and wherein theportions of said metallic strips within said thermostat are bentinwardly toward each other whereby said strips are normally spaced apartand whereby exposure of said thermostat to said predeterminedtemperature results in contact of said portions of said strips withinsaid thermostat. I

4. The fire alarm switch as set forth in claim 1 wherein saidelectrically conductive elements extending from said electrical switchare permanently affixed to said barb-bearing contacts.

5. The fire alarm switch as set forth in claim 4 wherein saidelectrically conductive elements are welded to said barb-bearingcontacts.

6. The fire alarm switch as set forth in claim 1 wherein said pair ofopenings extend into said electrical receptacle on opposite sides ofsaid transverse channel for receiving and holding a two-conductor wire.

7. The fire alarm switch as set forth in claim 2 including anelectrically nonconductive pin disposed between said heat distortablemetallic composition and said electrical switch.

8. The fire alarm switch as set forth in claim 1 including a thinmetallic plate operably mo'unted on said thermostat whereby heat on saidplate may be efficiently conducted to said thermostat.

1. A fire alarm switch adapted to be electrically connected in parallelbetween a pair of electrical conductors in a twoconductor wirecomprising, a thermostat operably connected to an electrical receptacle,said thermostat having a normally open electrical switch operablyconnected to heat sensitive means whereby exposure of said thermostat toa predetermined temperature will close said switch, said electricalswitch including a pair of electrically conductive elements extendingtherefrom into said electriCal receptacle, said electrical receptaclehaving a channel forming receptacle including base and closure membersadapted to be fitted together for forming a transverse channeltherethrough for receiving and holding a two-conductor wire, saidelectrical receptacle including a pair of barb-bearing electricallyconductive contacts, each one of said pair of barb-bearing contactsadapted to mechanically and electrically contact one of said conductorsin said two-conductor wire when said base and closure members are fittedtogether over a twoconductor wire positioned in said transverse channeltherebetween, said electrically conductive elements extending from saidelectrical switch in electrical contact with said barb-bearing contacts,and said fire alarm switch including a pair of spaced openings in saidelectrical receptacle positioned on the opposite side of said electricalreceptacle from said thermostat for receiving separate portions of atesting device for testing the electrical connections between saidelectrically conductive elements extending from said switch, saidbarb-bearing contacts, and the connection between said barb-bearingcontacts and said conductors.
 2. The fire alarm switch as set forth inclaim 1 wherein said heat sensitive means includes a heat distortablemetallic composition.
 3. The fire alarm switch as set forth in claim 1wherein said electrical switch includes a pair of electricallyconductive metallic strips extending from within to without saidthermostat, and wherein the portions of said metallic strips within saidthermostat are bent inwardly toward each other whereby said strips arenormally spaced apart and whereby exposure of said thermostat to saidpredetermined temperature results in contact of said portions of saidstrips within said thermostat.
 4. The fire alarm switch as set forth inclaim 1 wherein said electrically conductive elements extending fromsaid electrical switch are permanently affixed to said barb-bearingcontacts.
 5. The fire alarm switch as set forth in claim 4 wherein saidelectrically conductive elements are welded to said barb-bearingcontacts.
 6. The fire alarm switch as set forth in claim 1 wherein saidpair of openings extend into said electrical receptacle on oppositesides of said transverse channel for receiving and holding atwo-conductor wire.
 7. The fire alarm switch as set forth in claim 2including an electrically nonconductive pin disposed between said heatdistortable metallic composition and said electrical switch.
 8. The firealarm switch as set forth in claim 1 including a thin metallic plateoperably mounted on said thermostat whereby heat on said plate may beefficiently conducted to said thermostat.